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WATER CONSERVATION
TECHNICAL BRIEFS
TB 8 – Use of Drip Irrigation
SAI Platform
June 2010
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TB 8 – Use of Drip Irrigation
WATER CONSERVATION
TECHNICAL BRIEFS
TB 8 - Use of Drip Irrigation
Adopting more efficient techniques, such as using drip irrigation systems, can help
ensure that farmers use water more efficiently. Drip irrigation systems normally
place the water directly into the soil, or onto the soil surface, reducing the risk of
runoff and thereby improving water application efficiency. Drip irrigation systems
can be classified as traditional drip irrigation system, subsurface drip irrigation and
low cost alternative systems. For a well designed, installed, and maintained
irrigation system, application efficiencies can be up to 90 % for the area irrigated.
The structure of the technical brief is as follows: Sections 1 and 2 describe drip irrigation
systems. Section 3 sets out the key issues needed to work out before the farmer decides
whether a drip irrigation system is right for a particular farm. Section 4 presents a stepby-step
decision tree for the sustainable improvement of water efficiency at a farm
level. Section 5 outlines two case studies on drip irrigation implementation in Almeria,
Spain and Greece. Section 6 outlines a set of KPI to monitor drip irrigation efficiency.
Finally, Section 7 recommends some further reading.
Contents
Section 1: What is Drip Irrigation? ...................................................................................... 2
Section 2: Drip Irrigation systems ....................................................................................... 2
Section 3: Things to consider before installing a drip irrigation system ............................ 3
Section 4: A Pathway to improve irrigation efficiency ...................................................... 5
Section 5: Case Studies ....................................................................................................... 7
Section 6: Drip Irrigation systems KPI ................................................................................. 8
Section 7: References and Further Reading ....................................................................... 9
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TB 8 – Use of Drip Irrigation
SECTION 1: WHAT IS DRIP IRRIGATION?
The use of drip irrigation enhances irrigation efficiency relative to conventional
techniques (such as gravity systems, which include flood irrigation of entire fields, and
furrow irrigation using shallow channels or ditches to carry water to the crop). With
proper management, application efficiencies for a well designed, installed, and
maintained irrigation system can be in the range of 80 to 90 % for the area irrigated.
Without proper water management, they are typically 55 to 65 %. 1 Drip irrigation can
reduce exposure to water risks and input costs making an agribusiness operation more
resilient, profitable and solvent.
SECTION 2: DRIP IRRIGATION SYSTEMS
Drip irrigation systems can be classified as traditional drip irrigation system, subsurface
drip irrigation (SDI) and low cost alternative systems.
A traditional drip irrigation system contains a
main line and sub-main lines/header (to carry
water to drip lines), laterals or drip lines (to
distribute water to the outlets at base of plants),
emitters (outlets to plants), a pump or pressure
source, a control valve (to turn system on and
off), a check valve (to prevent backflow into water
source), a fertilizer injector (to apply fertilizer
Figure 1: Drip Irrigation System Example
directly into irrigation water), a filter and a
pressure regulator. More sophisticated system can include air vents, meters, timers,
controllers and/or drains.
A subsurface drip irrigation system is similar to the system described above; however
the irrigation of crops is conducted through buried plastic tubes containing embedded
emitters located at regular spacings. This system is less vulnerable to damage during
cultivation or weeding and it is unaffected by wind. In addition, places water close to the
rooting zone (limiting evaporative loss). 2 SDI is most widely used for the irrigation of
annual row and field crops in the United States. In Israel, SDI is widely used for the
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TB 8 – Use of Drip Irrigation
irrigation of permanent crops. Subsurface drip irrigation has been used in Arizona for at
least 25 years. However, its adoption has proceeded slowly for a high initial capital and
the intensive management needed. 3
Lastly, there are low cost alternative drip
irrigation system. One of these is called
Pepsee and is used in India. It does not
require micro tubes or emitters to place
water directly to the root zone instead the
lateral. 4 However, this system has a limited
life period, cannot withstand high pressure
of flow of water and supply an unequal
distribution of water. In Rajasthan and
Gujarat, local NGOs began promoting low
cost drip irrigation among cotton growers.
Farmers saw that by using pipes and
microtubes, they can water an acre of
cotton even with this restricted pumping
Drip irrigation was invented in Israel
in 1959 as a way of using more
efficiently the scarce resource. Since
then, Israeli farmers have refined
and automated the process, linking
data on temperature, radiation,
humidity and soil-water content to
not only control where water is
released, but when, and how much
is needed to meet a plant’s need for
transpiration.
time. Drip irrigation reduces the cost of cultivation, weed problems, soil erosion and
increases water use efficiency as well as electricity use efficiency, besides helping
reduce the overexploitation of groundwater. Recent times have seen a veritable
revolution in farmers adapting drip irrigation as a survival mechanism. 5 Yet in spite of
having many economic and other advantages, the growth of area under micro-irrigation
has not so far been appreciable compared to the total potential. 6
SECTION 3: THINGS TO CONSIDER BEFORE INSTALLING A DRIP
IRRIGATION SYSTEM
The key issues needed to work out before the farmer decides whether a drip irrigation
system is right for a particular farm are:
Quantity of water used for irrigation
Irrigation efficiencies
Water quality
Crops cultivated
Topography and physical site characteristics,
Source of the water supply
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TB 8 – Use of Drip Irrigation
Energy available
Operation and management skills
Farming equipment
Environmental concerns,
Costs.
The choice of the most suitable type
of drip system depends mainly on the
soil type (light or heavy soil;
infiltration rate, lateral moisture
movement), topography (slope), crop,
water quality. Drip irrigation systems,
however, are not suitable for all crops
and soil types. Drip irrigation is well
suited to multi-season cropping such
as soft and top fruit. Where it has
been used for field scale arable row
crops or vegetables, the cost and
practical issues of pipe installation and
retrieval currently challenge its more widespread adoption.
Unilever has successfully applied drip
irrigation system in tomato, gherkin and
tea crops in different part of the World.
The use of drip irrigation in Brasilian
tomato crops has cut water use by 30%,
boosted yields and also has helped to
reduce inputs of insecticide and fungicide.
In India, a drip irrigation trial in India
produced a water saving of 40% and also
cut chemical inputs in the gherkins
cultivation. a
Water quality is an equally important consideration when determining whether a drip
irrigation system is feasible. Surface water can contain organic debris, algae, moss,
bacteria, small creatures, weed seeds, and soil particles that can clog the emitters.
Clogging is the most serious technical problem in drip irrigation systems. However,
properly designed and maintained filtration systems generally protect the system from
most clogging. In general, adequate filtration, line flushing, and chemical treatment
prevent most clogging.
In addition, not all conventional fertilisers, herbicides, fungicides, and pesticides are
compatible with drip irrigation. Farmers need to consider alternative products and/or,
preferably, integrated pest management practices.
For drip irrigation to improve water efficiency use on farms, it is crucial to provide
regular system maintenance. This will include checking visually the system and the
emitter discharge, removing and cleaning the filters and valves, checking the pressure
system and the water flow rates. An Australian study showed that more sophisticated
irrigation systems and scheduling tools do not necessarily lead to better irrigation
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TB 8 – Use of Drip Irrigation
performance. However, frequent maintenance is essential to keep drip irrigation
functioning at design flow.
SECTION 4: A PATHWAY TO IMPROVE IRRIGATION EFFICIENCY
Water application efficiency is the ratio between the water used by a crop and the total
amount of water delivered to that crop, indicating how well an irrigation system
performs in transporting water to the plant roots. A strong contrast is apparent when
comparing furrows with sprinkler and drip systems, with the former having an efficiency
of around 55 %, sprinklers 75 % and drip systems 90 % 7 .
To improve water use efficiency, farmers need to consider multiple factors, and the
importance of each will depend on the operation’s particular circumstances.
Figure 2 illustrates a step-by-step decision tree for the sustainable improvement of
water efficiency on farms. Each factor is described in more detail below.
Figure 2: Step-by-step decision tree
A. Understanding the operation´s system
Understanding the operation’s system and specific circumstances is the critical starting
point on the pathway to improving water management practices and is key to
identifying the best suited irrigation equipment. Section 3 (above) lists the key factors
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TB 8 – Use of Drip Irrigation
famers need to consider. In addition, it is also important to consider the cost of
equipment, filtration, control, and numerous laterals needed.
B. Optimise the irrigation network and equipment
To optimise the irrigation network and equipment is necessary to control pressure,
water use and uniformity. The most widespread problem is low pressure, often the
result of extending irrigation schemes without paying sufficient attention to the impacts
of increased demand on pump capacity, the distribution network and equipment
performance. The result is poor application uniformity with knock-on effects on crop
yield and quality. As discussed above, proper maintenance and regular checks are
needed on pressure and volumes of water delivered to particular fields for comparison
with manufacturer’s guidelines for pumps and in-field equipment. In-field tests using
catch-cans can be used to check that correct equipment settings (e.g. sector angle, lane
spacing etc), water pressures and flow rates are being translated into a uniform
application of water across the field.
A sustainable drip system must be reliable and able to save water, increase yields,
manage salts, allow for crop rotation, and needed tillage operations.
C. Optimising the water management practices
This hinges on ensuring that water applications are managed (scheduled) according to
crop water requirements without unnecessary waste, i.e. avoiding over-irrigation and/or
surface run-off.
Most irrigators rely on their subjective experience to determine when it is right to
irrigate, usually by walking the crop and taking soil auger samples. However, to optimise
water use efficiencies, farmers should be encouraged to adopt a mix of both subjective
and more scientific scheduling techniques.
D. Demonstrating best practice
The final step on the pathway is to demonstrate ‘best practice.’ Some of the best
practices that have proved over time to lead to more efficient irrigation are listed below.
Calculate the plant water requirements and record the evaporation rate loss to
calculate the drip systems application
Rate irrigation highly within the operation’s management system
Know the farm soils – from an irrigation perspective
Design and maintain irrigation systems correctly
Monitor all aspects of each irrigation event
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TB 8 – Use of Drip Irrigation
Use objective monitoring tools to schedule irrigation
Use more than one method to schedule irrigation
Retain control of irrigation scheduling
Remain open to new information
SECTION 5: CASE STUDIES
Case study A: Primaflor Lettuce Farm, Spain
Primaflor farm, located in Almeria, produces different varieties of lettuces. To ensure
that irrigation is undertaken in the most efficient manner, the farm has integral soil
moisture meters within the growing crop to monitor soil moisture levels. These have
sensors which monitor moisture levels over the time in order to adjust irrigation
amounts from the pre-determined target levels. Any rise in moisture levels recorded at
the shows that the crop has been over irrigated and the technician will reduce the
subsequent applications of water to address this. 8
It can be 25% more efficient than other methods of irrigation as it does not incur the
losses through evaporation that topical applications of water are subject to.
The farm has gone one step further with the introduction of a pressure compensated
drip irrigation system, which is more expensive to purchase than the convention
drippers but provides a higher degree of accuracy over the conventional system. 9
Case study B: Greece
Greece has the highest population dependent on agriculture in Europe. Between 33-
40% of total agricultural area is under irrigation, mostly for crops (approximately 70%),
vines (4%) and trees (25%). Water is often supplied through public networks. Within
these networks, efficient irrigation technologies have not been widely adopted. While
surface water irrigation accounts for 35-40% and irrigation with sprinklers amounts to
50-55%, drip irrigation remains at 10% only.
There is significant scope, therefore, to improve water productivity at the farm level by
switching to more water efficient techniques or by improving current systems. In
Greece, for example, a significant proportion of cotton is grown using flood irrigation,
which requires 20000 litres of flood water to produce a kilogram of harvested crop due
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TB 8 – Use of Drip Irrigation
to high levels of surface runoff and evaporation. Drip irrigation of cotton can require
7000 litres per kilogram of crop, although that is still seven times higher than the
volume of water needed for the production of a kilogram of wheat. 10
SECTION 6: DRIP IRRIGATION SYSTEMS KPI
Water use (m 3 /Ton): Measure the water use of all irrigated water (water
that is either taken from the mains or from the environment and directly
irrigated or stored for future uses). A recording system should be
implemented so efficiency can be measured by m 3 of water per ton of
output.
Pumped water volume (m 3 /ha): A recording system should be
implemented so water pumped can be measured by m 3 of water per ha.
Field application efficiency (%): Field application efficiency is the ratio
between the water used by a crop and the total amount of water delivered
to that crop, indicating how well an irrigation system performs in
transporting water to the plant roots.
Total length of irrigation supply channel (each of lined and unlined) (km):
A recording system should be implemented to measure the length of
irrigation pipe network in kms.
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TB 8 – Use of Drip Irrigation
SECTION 7: REFERENCES AND FURTHER READING
Best Management Guidelines for Sustainable Irrigated Agriculture
http://www.maf.govt.nz/mafnet/rural-nz/sustainable-resource-use/irrigation/irrigationbest-management/finalwater05checked.pdf
This guide offers information about technical irrigation design and management factors.
Also provides information on how to plan, to operate and review a new irrigation
system.
USDA National Irrigation Guide
http://www.saiplatform.org/site_files/uploads/documenten/#16Nationalirrigationguide
USDA(Handbook).pdf
This guide offers a comprehensive and technical guide on irrigation system.
Water management toolkit for field crop growers
http://www.ukia.org/defra.htm
The toolkit comprises a booklet and series of spreadsheets that allow farmers to
schedule their irrigation more effectively.
Waterwise on the farm
http://www.environmentagency.gov.uk/static/documents/Research/geho0307blvhepweb_432285.pdf
Water Efficiency Tool
http://www.envirowise.gov.uk/uk/Our-Services/Tools/Water-Efficiency-Tool.html
A series of modules providing guidance and call to actions for water efficiency.
Drip Irrigation Design Tutorial
http://www.irrigationtutorials.com/index.htm#sprinkler
This tutorial provides a guide to design a simple drip irrigation system for small farms.
1 www.wsi.nrcs.usda.gov/.../Irrigation/National%20Irrigation%20Guide.pdf
2 Irrigation Best Practice A Water Management Toolkit for Field Crop Growers. ww.defra.com
3 http://ag.arizona.edu/crop/irrigation/azdrip/SDI.htm
4 www.iwmi.cgiar.org/iwmi-tata_html/PM2003/PPT/.../Pepsee.ppt
5 http://www.iwmi.cgiar.org/Publications/Water_Policy_Briefs/PDF/wpb03.pdf
6 http://www.iwmi.cgiar.org/Publications/Other/PDF/Paper%2015%20of%20NRLP%20series%201.pdf
7
EEA, Water resources across Europe, Confronting Water Scarcity and droughts
http://www.eea.europa.eu/
8 http://www.flagshipfarms.eu/downloads/case_lettuce.pdf
9 http://www.flagshipfarms.eu/case5.php
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TB 8 – Use of Drip Irrigation
10 Chief Liquidity Series - Issue 1: Agribusiness (geography- and sector-specific water materiality briefings
for financial institutions) http://www.unepfi.org/fileadmin/documents/chief_liquidity1_01.pdf
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